Shear-extrusion method

Abstract

A shear-extrusion method of severe plastic deformation for fabrication of metal shapes with ultra-fine structures is described. The improvements of the method include unidirectional shear of any required intensity during one step processing and under high hydrostatic pressures, fabrication of long products with different cross-sections, refinement of low ductile alloys, the increase of productivity and cost reduction. The method can be realized as forward extrusion, backward extrusion, semi continuous extrusion and extrusion of hollow shapes in portal dies with a welding chamber.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 512,260 filed Oct. 20, 2003, the entire speciflcation of which is expressly incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to severe plastic deformation of metals and alloys to control their structure and properties.[0004]2. Description of the Prior Art[0005]It is known in the art that severe plastic deformation performed by simple shear results in refinement of grain structures to the sub-micron, sometimes to nano scale. That leads to significant improvements in many physical and mechanical properties such as strength, ductility, fatigue, corrosion resistance, super plasticity, etc. Different processing methods were developed for intensive plastic deformation. Most of them are restricted by small sample sizes or soft materials and are used as a laboratory tool: high pressure torsion (P...

AI Technical Summary

Benefits of technology

"The invention is a method of severe plastic deformation to create high strains during one step processing for structure refinement. The method involves using the shear-extrusion method to simultaneously form long products of different shapes. The method includes steps of providing cylindrical billets, preheating, placing in a container, forcing through an extrusion die, controlling extrusion and angular speeds, and repeating for subsequent billets. The method can be used with various materials such as aluminum alloys, magnesium alloys, titanium alloys, and powders. The method also includes controlling the billet preheating temperature and extrusion speed to achieve the desired strain and temperature during the extrusion process. The invention also includes tools for forward and backward shear-extrusion, as well as a die for shear-extrusion of hollow shapes. The technical effects of the invention include achieving high strains during structure refinement and simultaneous formation of long products of different shapes."

Problems solved by technology

In result, such processing is time and labor consuming with a high product cost.

In most cases, their conversion to final products presents additional problems with the increase in the cost.

However, the only known method in the art for such products is superplastic extrusion (see U.S. Pat. No. 5,620,537).

The second step should be realized with very low strain rates or high temperatures that leads to low productivity and degradation of the material structure and properties.

Therefore, the known method does not provide evident technical benefits and did not find practical applications.

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